The invention relates to a liquified gas-containing generator for an inflatable impact protection cushion for protecting a motor-vehicle occupant against injury.
With passive safety devices for motor vehicles in which driver and passenger are protected by inflatable impact protection cushions (also called airbags) against injury as a result of impact against the steering wheel or instrument panel, use is generally made of gas generators with a fixed propellent-charge unit for the purpose of gas generation. In this connection, use is made, for example, of a material based on sodium azide. A definite disadvantage of such gas generators is that the cinder particles arising in the course of combustion have to be retained by rather elaborate filter packets in order not to impinge, together with the combustion gases, upon the inside of the impact protection cushion, as a result of which the cushion could be damaged. For the purpose of additional protection against damage by means of particles the impact protection cushions are in part coated on the inside. As a result, the material for the impact protection cushion has more resistance to bending and can be accommodated less well and in less compressed manner in the module or container.
Efforts have recently been made to provide passive safety devices for motor vehicles of the above type equipped with liquified gas-containing generators. No solid particles arise in the course of combustion of the liquified gas, so that it is possible to do without filter packets. Accordingly it is also possible to do without an inner coating of the impact protection cushion. Together these two factors lead to reductions in weight and in space requirement of such devices.
So that gas generators only emit their combustion gases above a definite internal pressure and hence in reproducible and controlled manner, it is known to provide membrane-like elements which burst open above a definite pressure. By means of such membranes it is also possible to adjust the gas-generation rates and the time delay after which the impact protection cushion is inflated following triggering of the crash sensor. For safety reasons it is advantageous if this membrane-like part of the gas generator is only pressurized when the gas generator is ignited and if it is not under pressure when the gas generator is not ignited.